1. Field of the Invention
The present invention relates to an image display device used for viewing an image etc. in an image pickup apparatus such as a video camera, an image pickup apparatus provided with this, and an image display method.
2. Description of the Related Art
In recent years, a camera-integrated recording/reproducing device (it is also described as a “camcorder”, hereafter) that unifies a camera and a recording/reproducing device becomes widespread as a device that picks up moving images. The camcorder records subject images picked up by a camera into a recording medium while checking by a user on a small-sized monitor of a recording/reproducing device, and reproduces on the small monitor.
As a recording medium, although a magnetic tape was common conventionally, it is now replacing to mediums, which are smaller in size and higher in density, such as an optical disk, a hard disk drive, and a semiconductor memory. Accordingly, the size of a camcorder body is also decreasing.
The image picked up by the camcorder is appreciated mainly with a television for home. Since a high-definition television with a large screen is spreading as a television for home, a recording format of the camcorder is becoming to the high-definition format in order to satisfy a requirement to appreciate with the large screen. However, when the high-definition signal with high-resolution is reproduced on a large-sized screen, defocus of an image is significantly conspicuous as compared with a case when a low-resolution signal is reproduced on a small-sized screen.
As a monitor device (an image display device) for checking an object image at the time of shooting, a small-sized liquid crystal display monitor of which size is about three inches is used according to the size of the camcorder body. A resolution of such a small-sized liquid crystal display monitor is only a QVGA (Quarter Video Graphics Array: 320*240 pixels) class that does not have a quality sufficient to display the high-definition and high-resolution signal. Therefore, the small-sized liquid crystal display monitor is unsuitable for delicate focusing.
Then, a technique for assisting focusing is proposed. For example, Japanese Examined Patent Publication No. H06-028392 (JP H06-028392B) discloses a technique that colors an emphasized edge signal to emphasize an edge of a video signal.
When high-frequency components of a video signal is emphasized, an edge of a focused subject picture, i.e., a video signal with a clear edge, is further emphasized, because the edge includes many high-frequency components. On the other hand, since a defocused subject picture includes a few high-frequency components, an edge is not emphasized even if the high-frequency components are emphasized. Therefore, when paying attention to the edge portion of the video signal of which the high-frequency components are emphasized, it is easy to determine which portion is focused, because appearances are different depending on focusing conditions.
However, since a small-sized liquid crystal display monitor has a narrow dynamic range, the video signal of which the amplitude is more than a certain level is saturated. Therefore, when the amplitude of an edge correction signal that emphasizes the edge portion of the subject exceeds a threshold value for the saturation, the video signals are expressed as the same amplitude regardless of the amplitude of the edge correction signal. Therefore, the focused subject picture cannot be distinguished from the edge correction signal of the defocused subject picture. As a result, there is a problem that a user is difficult to focus.